Fig. 4 Cardiac oxygen indices from non-invasive vs. invasive arterial pressure. Noninvasively (NAP) and invasively (IAP) derived cardiac oxygen indices in Bland and Altman fashion. Please note that the horizontal and vertical axes have the same scale so that the differences can be easily assessed relative to the average values. DTF: diastolic time fraction; Adia/Asys: ratio of diastolic and systolic areas; RPP: rate pressure product